z=2-(x^2+y^2)z'x=-2x z'y=-2ydS=√(1+4x^2+4y^2)dxdy,∑在xoy平面的投影x^2+y^2=2A=∫∫√(1+4x^2+4y^2)dxdy （下面用极坐标=∫(0,2π)dθ∫(0.√2)r√(1+4r^2)dr=(π/4)∫(0.√2)√(1+4r^2)d4r^2=(π/4)(2/3)(1+4r...我们这同学做的一个结果是 8根号2π/3 一个是13π/3. 哪个对呀。。=(π/4)(2/3)(1+4r^2)^(3/2)|(0,√2)=(π/6)(27-1)=13π/3 13π/3是对的